The mechanisms of drug and hormone action on glycogenolysis will be investigated using a single gene, sex-linked variant (carried in I strain mice) that results in a marked deficiency in phosphorylase b kinase (PBK) activity to less than 5% of that in extracts of comparable muscles of control mice, C57BL or Swiss-Webster. Yet epinephrine and isoproterenol stimulate glycogenolysis (and phosphorylase a formation) in isolated hemidiaphragms of this pharmacogenetic variant, but the concentration dependence differs from that of C57BL. The concentration-dependence and time course of biochemical changes that may be important in regulating isoproterenol-stimulated glycogenolysis will be compared in I and C57BL hemidiaphragms. These include: phosphorylase b to a conversion; changes in muscle cyclic AMP, glucose-6-P, ATP, and 5'-AMP concentrations and conversion of phosphorylase kinase from a nonactivated to an activated form. Isoproterenol-stimulated glycogenolysis and phosphorylase b to a conversion will be compared in quiescent and contracting muscle using electrically stimulated isolated diaphragm preparations. Isoproterenol-stimulated glycogenolysis will also be compared in I and C57BL skeletal muscles with differing activities of the glycogenolytic enzymes, including the gastrocnemius, gracilis, and soleus muscles. The biochemical changes associated with the glycogenolytic response in intact I muscle will be correlated with the regulation of glycogenolysis in the protein-glycogen complex (isolated by differential centrifugation of skeletal muscle extracts) to aid in elucidating the mechanisms involved. The nature of the phosphorylase kinase deficiency mutation will be further investigated by purifying and characterizing the mutant phosphorylase kinase, which is present in I strain skeletal muscle in approximately normal amounts. The rate of synthesis and degradation of phosphorylase kinase and phosphorylase will be compared in I and C57BL skeletal muscle.